i have Yukon XL 1500 5.3 LITER ENGINE. STARTED LOSING OIL PRESSURE SO I CHANNGED THE SENDING UNIT AND THE OIL PUMP BUT STILL HAVE THE SAME ISSUE.

How you measures the oil pressure with a gauge that has a hose that threads into the block where the sender goes.

I have a 2008 Yukon xl with a 6.2 liter. Was losing oil pressure sometimes, but not always. Was getting Red light warning about no pressure and to shut engine off. On highway, lifters would rattle and pressure would drop. Then, it may go 500 miles with no error warning. Dealer changed sending unit, checked oil pump, and then wanted to change some other parts for around $1200.00.I had already paid them several hundred. Service manager told me they could not guarantee this would fix problem. I did Google search and found several people had similar issues. I had a local garage change the rubber grommet on oil pickup tube. Was less than $500.00. Completely cured problem.

Put card board under truck trak the leak take a picture.go auto parts store with picture.you might just have a bad gauge,even though you have a leak